This invention relates generally to injection blow-molding machines, and more particularly to a type thereof wherein the formation of parisons is substantially improved.
In the technique of blow-molding, there are two types of metal molds forming parisons having bottoms, one being an integral mold and the other being a separable mold. In the former type metal mold, the parison having bottom formed in a portion thereof is drawn out in the axial direction into a blow-molding portion of the metal mold to be blown into an article. On the other hand, in the latter type metal mold, the parison formed therein is removed from the separable metal mold in a direction perpendicular to the axis of the parison and thereafter blown into an article.
Heretofore, difficulties have been experienced in the formation of parisons in the separable type injection metal mold employing a hot-runner. Parisons thus formed tend to be deformed or damaged at their bottoms at the time of the removal from the metal mold, and hence the productivity of this kind of machines has been extremely low.
Furthermore, because a hot-runner block is directly coupled to the fixed side of the injection metal mold, the temperature of the parison at the side contacting with the fixed mold-half becomes higher than the other side contacting with the movable mold-half, thus causing uneven blowing of the parisons.
To eliminate this difficulty, it has been attempted to separate the hot-runner block from the fixed mold-half by means of a hydraulic cylinder or the like and to attach the hot-runner block to the fixed mold-half only while the injection takes place. However, this makes the metal mold too much complicated and hence is found to be impracticable.